1. Field of the Invention
This invention relates to a slit illuminating apparatus used for ophthalmic clinical examination or the like.
2. Related Background Art
A slit lamp is an apparatus for applying a slit-like light beam to a conjunctiva, a cornea, a chamber angle, a crystalline lens, a vitreous body, an eye fundus or the like to observe an eye to be examined directly by means of a finder or indirectly through a monitor. In the slit illuminating apparatus according to the prior art, a slit-like light beam is projected from one direction and therefore, depending on the direction of observation, it is difficult to see the eye to be examined and it is necessary to rotate the entire slit illuminating optical system about the eye to be examined each time, and this is cumbersome. Further, with this prior art apparatus, it is impossible to set two directions at time and turn on the apparatus alternately to analyze the shape of the eye to be examined from the difference in contrast or to illuminate the eye to be examined from two directions at a time to confirm the whole aspect, and further to reproduce the two directions when illuminating.
As shown in Japanese Laid-Open Patent Application No. 34529/1987, there is known a slit projection apparatus for projecting a slit image onto an eye to be examined at a variable angle of elevation, but in such apparatus, a mirror and a lens are varied or a polarizing prism for forming a particular direction of application is used and it is impossible to irradiate the eye to be examined simply from any different direction of application.